Marine fish represent some of the most diverse life forms on earth. With the world's oceans covering approximately 66% of the earth's surface, they provide the perfect domain for an incredibly diverse variety of fish species. Within the marine aquarium trade, it is possible to obtain and successfully keep species as varied as the delicate Mandarin Goby all the way to apex ocean predators in the form of reef sharks. The options within the marine aquarium hobby for varied shapes, colors and sizes of fish are almost limitless.